I am not trying to start an argument. I am looking for knowledgeable answers and factual data. Right now my car has a 76mm master power turbo with a 3" downpipe running to a 3"-2.5" y with 2.5" magnaflow tail pipes and magnaflow mufflers. I am entertaining the idea of going to a pt88 which has a 4" exhaust vband flange. As far as flow is concerned, will I need a 4" down pipe and to run it all the way to my tail pipes or what? Can I adapt the 4" down to 3" and use my existing down pipe. Right now I don't plan on pushing any more boost. Probably less boost honestly as I am limited to a certain hp number. Looking for some real world knowledge here on this.